1. Field of the Invention
The present invention relates to liquid-jet heads for ejecting, methods of fabricating the same and liquid-jet apparatuses. More specifically, the present invention relates to an ink-jet recording head for ejecting ink droplets out of nozzle orifices by applying pressure to ink supplied to pressure-generating chambers communicating with the nozzle orifices for ejecting the ink droplets by use of piezoelectric elements, a method of fabricating the same and an ink-jet recording apparatus.
2. Description of the Prior Art
Typical ink-jet recording heads include vibration plates, which constitute part of pressure-generating chambers communicating with nozzle orifices for ejecting ink droplets. Such ink-jet recording heads eject ink droplets out of the nozzle orifices by deforming the vibration plates with piezoelectric elements and thereby applying pressure to the ink in the pressure-generating chambers. There are two types of the ink-jet recording heads currently put into practical use; one uses a piezoelectric actuator of a longitudinal vibration mode, which expands and contracts in an axial direction of the piezoelectric element, and the other uses a piezoelectric actuator of a flexural vibration mode.
The former type effectuates variation of volumes of the pressure-generating chambers by allowing end faces of the piezoelectric elements to abut on the vibration plates. Accordingly, it is possible to fabricate a head suitable for high-density printing. However, the former type has a problem of complicated fabrication process, because the fabrication process includes a difficult step of sectioning the piezoelectric elements into comb shapes so as to align with arrangement pitches of the nozzle orifices, and an operation for positioning and fixing the sectioned piezoelectric elements to the pressure-generating chambers.
On the contrary, the latter type effectuates formation of the piezoelectric elements on the vibration plates by a relatively simple step of attaching a green sheet of a piezoelectric material in line with shapes of the pressure-generating chambers and then baking the green sheet. However, the latter type has a problem of difficulty in high-density arrangement, because a certain area is required for utilizing flexural vibration.
Meanwhile, in order to solve the inconvenience of the recording head of the latter type, Japanese Laid-Open No. 5(1993)-286131 discloses a recording head, in which a piezoelectric material layer is formed uniformly on an entire surface of a vibration plate by use of a film forming technology, and piezoelectric elements are independently formed for respective pressure-generating chambers by sectioning the piezoelectric material layer into shapes corresponding to the pressure-generating chambers by use of a lithography process.
Moreover, such an ink-jet recording head is provided with a reservoir as a common ink chamber to the respective pressure-generating chambers, whereby the ink is supplied from the reservoir to the respective pressure-generating chambers.
Such a reservoir has been conventionally formed on a passage-forming substrate, where the pressure-generating chambers are formed, on an opposite side to the piezoelectric elements, by means of laminating a plurality of substrates. However, there has been a problem of increases in material costs and assembly costs. In addition, there has been a problem of difficulty in downsizing the head. In order to solve the foregoing problems, a structure is proposed in which a reservoir is provided on the same side of a passage-forming substrate where piezoelectric elements are formed and the reservoir communicates with pressure-generating chambers via penetrated portions formed on vibration plates.
However, in the above-described ink-jet recording head, the penetrated portions are formed by mechanically processing the vibration plates. Accordingly, there is a problem that cracks or the like are generated around the penetrated portions. Moreover, there is also a problem that fragments may fall from a portion of the vibration plate where cracks are generated if ink is filled in and ejected in the state where the cracks are generated, whereby the fragments may occlude a nozzle orifice and may cause imperfect.
Note that the foregoing problems are not limited to ink-jet recording heads for ejecting ink, but are also applicable naturally to methods of fabricating other liquid-jet heads for ejecting liquids other than ink.